31-03-2015

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DONORA AIR POLLUTION DISASTER & ARSENIC GROUNDWATER POLLUTION

Dr. S. Mohana Roopan

DONORA AIR POLLUTION DISASTER

Donora, located in Pennsylvania, is a small town rich in factories like steel mills, zinc smelters and sulphuric acid plants.

On October 25th 1984 a four day smog occurred. This was due to anticyclone conditions that gave rise to no air movement

and in turn temperature inversion had taken place. (The condition when the cold layer is trapped below the warm layer is called

temperature inversion). Donora lies at the bottom of a valley with hills surrounding it on each side of

the river.

Due to accumulation of cold air (because of inversion) at the bottom of the valley, fog was formed and was persistent for four days.

Moreover, the fog layer was so thick that it reflected all solar radiationsduring the day so heat received was not sufficient enough to break this inversion. And during night the upper layer would further cool and stabilizethe inversion.

The deadly pollutants emitted by the industries were trapped and concentrated in the smog and remained there for 4 days.

Out of a population of 14,000; 6000 townsmen fell ill and 20 of them died.

31-03-2015

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ARSENIC POLLUTION IN GROUND WATER

West Bengal and Bangladesh are heavily contaminated by the toxic element Arsenic.

In West Bengal (1978) and Bangladesh (1993) it was found to be more widespread than previously assumed.

Local people were found to be ingesting low doses of arsenic for 10-14 years.

This lead to Melanosis (white or black spots mottle the skin) which ultimately evolved in Leprosy that would rot into ulcers.

Long exposures led to bladder and lung cancer.

Children affected greater by arsenicosis. The affected people were socially isolated, not allowed to attend schools and unable to marry and ultimately lead to broken marriages.

According to WHO the maximum permissible levels are 10mg/L of arsenic. In West Bengal 40 million out of 90 million are feared to have had exposure

due to the contaminated water. Many districts in Kolkata lie in the Arsenic Risk Zone. Arsenic eventually seeped into the ground water in the Ganga Delta. Overuse of Arsenate and Copper Arsenite as pesticides (for summer paddy

and jute) are the major causes of this. As a protective measure contaminated tubewells are painted red and safe

tubewells are painted green.

THANK YOU